1. Field of the Invention
The present invention relates to a vacuum processing apparatus having a vibration dampening mechanism and, in particular, to a substrate bonding apparatus for a liquid crystal display device.
2. Description of the Related Art
The substrate bonding device for the liquid crystal display device is constructed such that the alignment marks of a pair of substrates are read by CCD cameras or the like in the vacuum chamber and, based on the result, the positions of a pair of substrates are corrected and the substrates are then bonded together (see Japanese Unexamined Patent Publication No. 2001-305563 and No. 2002-229044, for example). In the substrate bonding device, a vacuum chamber and a vacuum pump are connected by a pipe so that the vacuum chamber is evacuated (pressure is reduced) by the vacuum pump.
In the case where the substrates are small in size, the volume of the vacuum chamber is small and, therefore, a vacuum pump having smaller displacement can be used. In such a case, the vibration of the vacuum pump has no effect on the vacuum chamber. In the case where the accuracy of bonding the substrates is not extremely high, the vibration transmitted from the vacuum pump to the vacuum chamber has substantially no effect on the operation of bonding the substrate.
In fabricating a liquid crystal display device, a plurality of substrates corresponding to a plurality of liquid crystal panels are acquired from one glass substrate. In order to reduce the unit price of each liquid crystal panel, the glass substrate size has been increased to allow as many liquid crystal panel substrates as possible to be obtained from a single glass substrate. With the increase in the size of the glass substrate, the equipment for processing the glass substrates has been proportionately increased in size, with the result that the substrate bonding device in which the alignment marks are read by the CCD cameras or the like in vacuum and the substrates are bonded together poses the problem described below.
An increased size of the glass substrate increases the volume of the vacuum chamber, and therefore requires a vacuum pump of a large displacement to increase the throughput. However, this poses the problems of a larger vibration of the vacuum pump which is transmitted to the vacuum chamber through a vacuum pipe, and the resulting vibration of the CCD cameras and the glass substrate in the vacuum chamber makes the alignment operation impossible, thereby leading to the problem that the throughput is reduced due to the deviation of the substrate bonding and the retries of the alignment operation.
A flexible pipe of a bellows type is sometimes connected as a part of the pipe connecting the vacuum chamber and the vacuum pump. The flexible pipe has the function of suppressing the transmission of vibration from the vacuum pump to the vacuum chamber. In the case of a vacuum pump of a large displacement, however, the vibration transmission damping function of the flexible pipe transmission has no great effect of suppressing the vibration transmitted. The use of a long flexible pipe would lengthen the evacuation time due to an increased evacuation gas resistance, resulting in an adverse effect on the throughput. Also, a long flexible pipe connected cannot effectively suppress the vibration transmission.
Further, as the pattern on the liquid crystal display device becomes more and more detailed, demand has increased than ever before for a higher accuracy of the substrate bonding in the substrate bonding apparatus.
In this way, in the vacuum processing apparatus comprising a vacuum chamber, a vacuum pump and a pipe connecting the vacuum chamber to the vacuum pump to evacuate the vacuum chamber, the problem is that the vibration of the vacuum pump is transmitted to the vacuum chamber and adversely affects the processing in the vacuum chamber.